A common procedure in circuit board processing involves laminating multiple cores together. However, generally, the cores are not electrically connected via to via during lamination. For example, one method involves first electrically connecting the cores using conductive pads. After lamination, a hole is drilled through the conductive pads and electroplated with copper to form the via.
An alternative solution uses conductive adhesive to electrically attach vias during lamination. The conductive adhesive is placed onto a via and electrically connects the vias when the cores are laminated together. However, conductive adhesives contain plate-like structures greater than 0.5 mils in size. These plates tend to clog at the top of the holes. Therefore, the adhesives cannot be used effectively with thicker cores and smaller vias. Additionally, conductive adhesives require precious metal for good connections, making the products more expensive. Finally, a substantial number of manufacturing sites are not equipped to handle conductive adhesives. Consequently, significant costs may be required to modify current manufacturing sites to use conductive adhesives.
As a result, there exists a need for a structure and method of attaching cores having vias with conductive surfaces without using a conductive material for the joining process such as that that is currently used.